Charities are calling for improved mental health provision in schools as new figures reveal more than 50,000 children and young people contacted Childline last year seeking help for serious mental health problems.

The helpline has seen a 36% rise over four years in youngsters needing help for depression and other disorders, while there was also a rise in the number of youngsters feeling suicidal.

Figures from the National Society for the Prevention of Cruelty to Children (NSPCC) reveal 50,819 children and young people in 2015/16 received counselling for a serious mental health issue – a rise of 8% over four years.

Those aged 12 to 15 made up a third of the sessions, with girls almost seven times more likely to seek help than boys.

Peter Wanless, chief executive of the NSPCC, said the figures, released at the start of Children’s Mental Health Week, were deeply concerning.

He said: “To ensure the next generation aren’t left to deal with a mental health epidemic, there has to be a much more comprehensive network of professional support and treatment in place that is easily accessible for young people who are desperate for help to get their lives back on track.”

Sam Royston, director of policy and research at the Children’s Society, said it was desperately worrying that so many young people were experiencing problems.

She said: “Whilst such issues may affect any child, in our own research, we have found there is a widening gap between the wellbeing of adolescent girls and boys.

“Many factors may contribute to this – for example we have found that adolescent girls are particularly likely to experience emotional bullying such as name-calling.”

She added: “Failing to address mental health problems early on can severely damage the lives of young people. As a first step all children should be able to access mental health and wellbeing support such as counselling in schools so they get support early to prevent a problem becoming a crisis.”

Childline said early signs of a serious mental health problem in children and young people include becoming withdrawn from friends and family, being tearful or irritable, sudden outbursts, and problems eating or sleeping.

One 16-year-old girl told Childline: “I want to know what’s wrong with me. I have been seeing a counsellor about my mental health issues recently but they just told me to eat and sleep better and forget about the past, which didn’t help me at all.

She added: “I wish I could speak to someone who actually cared about me and I felt comfortable talking to.”

Another young person said: “I’m struggling to cope with bipolar. One minute, I feel so low, like I’m trapped, and all I want to do is disappear. Then suddenly, I feel the complete opposite, and I’m really happy and I start thinking about everything in a really positive light. I feel like I push away everyone that tries to help, I tell them I hate them and blame them for everything. I just feel like I’ve turned into a monster.”

Childline founder Dame Esther Rantzen said: “It’s striking how many more children seem to be suffering serious mental health problems today than when we launched Childline 30 years ago.

“So many desperately unhappy children seem to be suffering suicidal thoughts, self-harming, becoming anxious and depressed, with many of them turning to Childline because no other support is available.”

Rantzen said children’s mental health services are already “terribly overstretched” with young people unable to access the professional help they need.

She said: “We believe there needs to be far more emphasis on providing help for these children as they struggle to deal with what are very serious illnesses.”

Sarah Brennan, chief executive at the charity YoungMinds, agreed more support for young people was vital, especially from schools.

She said: “Young people face a huge range of pressures including stress at school, college, university, body image issues, bullying on and offline, around-the-clock social media and uncertain job prospects.

“Difficult experiences in childhood including bereavement, domestic violence or neglect can also have a serious impact on mental health.”

Brennan added: “As a society we need to do far more to prevent mental health problems from developing in the first place. To start with, we urgently need to rebalance our education system, so that schools are encouraged to prioritise well-being and not just exam results.”